Cytochalasin B (CB) inhibits sugar transport in mammalian cells and affects cell structure and motility in a wide variety of cells and tissues. We have previously found that (3H)CB binds to high affinity and low affinity binding sites in mammalian cells. The high affinity sites are further divided into those which are related to sugar transport and those which are not; the biological function of the latter is unknown. In the proposed research, we plan to identify, isolate, and characterize all three types of CB receptors. Experiments to be included are (1) synthesis and chemical characterization of CB derivatives with different biological activities, (2) quantitative studies on the effect of CB and related compounds on sugar transport and on a variety of motile systems, (3) characterization of cellular receptors for CB, (4) studies on the interaction of CB with isolated membrane fractions and contractile proteins, and (5) utilizing CB binding to study changes in sugar transport activity, motility, and microfilament distribution in mammalian cells at different physiological states (e.g. after viral transformation) and at different stages of development. The main objectives of the proposed research are: (1) elucidation of the molecular basis of action of CB and related compounds, (2) increasing our knowledge on cellular components involved in sugar transport, cell structure, and cellular contractility and motility, and (3) developing CB and related compounds into useful tools for biological and medical research.